This invention deals with a ceramic fiber reinforced refractory product and a method for introducing ceramic fibers to a refractory material.
In the past concrete and refractory materials reinforced with metal in various forms have been described in the art which enhance the strength properties of the concrete or refractory into which they are incorporated.
In U.S. Pat. No. 3,429,094 to J. P. Romualde, for example, a two-phase material is described comprising steel wire within concrete, the wires being spaced not in excess of 0.5 inches to increase the cracking strength of the concrete. The material is prepared by mixing proportions of short pieces of wire directly with cement, sand and water or pouring a fluid mix of concrete around long pieces of wire. Similar wire reinforcing elements are described in British Pat. No. 515,003.
In U.S. Pat. No. 2,677,955 to G. Constantinesco a reinforced concrete material is described comprising a three dimensional and uniformly distributed mattress of wire comprised of short coils of helical elements in a hardsetting cement mass.
In U.S. Pat. No. 1,633,219 to G. C. Martin, a plastic material for forming a pipe is provided having mixed therein small lengths of iron, steel, or other metals, preferably pieces of wire, 1 to 4 inches in length, plain or crimped.
Other metal reinforcing elements have been described such as continuous metal elements in the form of sheets of layers connected together by fine metal wires twisted together as in U.S. Pat. No. 1,389,942, ribbon-like strips or shreds of iron and steel as per British Pat. No. 303,406 and thin metal bars as in British Pat. No. 799,860.
Steel fiber reinforcing elements about 1/2" in length for concrete have also been described in British Pat. No. 252,975 comprising a length of wire or strip with deflected or extended ends which can be incorporated in concrete by addition or mixing with the aggregate, sand, cement and water forming the concrete.
Although metal additions to concrete or refractory materials enhance the strength properties of such materials, the reinformed products, by virtue of such metals, are susceptible to corrosion and loss of strength properties at high temperatures. Ceramic materials, such as ceramic fibers, are resistant to corrosion and maintain their strength properties at high temperatures making them ideally suited as substitutes for metals as reinforcing elements for refractories and other materials. Heretofore ceramic fiber reinforcement of refractories could not be successfully accomplished because of fiber breakage during incorporation and the difficulty of uniformly distributing the fiber in the refractory matrix during mixing.
The present invention solves the problem of ceramic fiber addition to materials such as concrete or castable refractories by employing a ceramic fiber in yarn form which is resistant to abrasion, breakage or surface flawing and can therefore be combined with the material to provide reinforcing properties. The result is a reinforced product having excellent strength and crack resistant properties even at high temperatures.
By employing the method of this invention such ceramic fibers are uniformly dispersed in the material matrix without substantial damage to the fiber's integrity.